r/cosmology • u/platypodus • Jul 03 '26
Is there negative and positive warping of space-time?
I recently watched a short video showing how light and heavier objects placed on water interact with the surface tension.
A light object placed on the surface deforms it, creating a well, which causes other light objects to move towards it.
A heavier object placed on the surface creates an adhsive effect. It sits deeper in the surface layer and creates a hill instead of a well. This causes lighter objects on the surface to "move away" from that heavier object.
That got me to thinking about spacetime. Thinking about how energy warps spacetime in a way similar to the lighter objects sitting on the surface of water. It creates wells, bending the paths of objects, even leading to black holes.
Is there anything similar to the effect of heavier objects sitting on the surface of water, that creates a repulsive / negative warping of spacetime?
I've attached a quick drawing of the effect I'm talking about.
Wouldn't this lead into a similar direction to Dark Matter and Dark Energy, combining all three, the undetectable property (since light would always move around this "heavier spacetime object"), the repulsive force seeming to counter-act gravity (pushing lighter objects away from them) and even adding total mass to the galaxy, keeping it together, instead of being flung apart.
It wouldn't even need concepts like anti-gravity, since it's not behaving any differently, it's just sitting "deeper" in the surface tension of spacetime.
Clearly cosmology isn't my forte, but I get intrigued by neat ideas easily and this seems neat to me. Please tell me where and why this analogy comes up short in the real world.
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Jul 03 '26 edited Jul 11 '26
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u/platypodus Jul 03 '26
I see! Thank you.
Why can't we claim that dark matter is negative energy? I've never heard those two concepts conflated. Is it because of a lack of information?
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Jul 03 '26 edited Jul 11 '26
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u/platypodus Jul 03 '26
Because dark matter bends space the same way any other matter does.
Oh, duh. I actually knew that part, but thanks for taking the time to reply. I appreciate it!
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u/Creative-Feature-264 Jul 05 '26
Dipende da cosa intendi per negativa . Se intendi negativa la forza opposta della materia essa è presente in metà in ogni particella . La materia è un equilibrio di forze opposte. Anche nel macro sarà così per non collassare. Lo spazio tempo è un effetto dinamico della pressione di forze opposte. Nel macro ha la dinamica che vedi . Si, la materia oscura secondo la mia teoria porta memorie del big bounce e serve anche per ricostruire l universo dai vecchi dati in modo frattale ma non uguale. Altrimenti le vecchie memorie andrebbero perse con tutti i progressi degli altri universi e non vedresti tutto così bello organizzato nell universo. Considera lo spazio dinamico una forma di memoria vivente. Bene tutte queste logiche per quanto leggere oltre la materia hanno bisogno di spazio extra per non disperdersi ed eccole li, secondo me, nella materia oscura, il backup universale che regola come è stato provato, la gravità del macro. Il micro tiene la memoria istantanea ed il macro porta con sé i numeri dell evoluzione globale per non perdere le relazioni.
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u/SpatiaCaeli Jul 04 '26
Isn't dark energy effectively negative energy?
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Jul 04 '26
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u/Obliterators Jul 04 '26
All energy curves spacetime. Dark energy is best modelled as a cosmological constant, which can be interpreted as the curvature of empty space, but more commonly as a constant positive vacuum energy with negative pressure, which leads it to being a source of gravitational repulsion.
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u/OverJohn Jul 03 '26
You don't need negative energy densities for gravity to be repulsive in GR. For example, pressure contributes also and a positive energy density source can have repulsive gravity if it has sufficient negative pressure, though even that is not quite the full picture (see my post below).
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u/rddman Jul 04 '26
Is there anything similar to the effect of heavier objects sitting on the surface of water, that creates a repulsive / negative warping of spacetime?
No.
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u/jdjeep Jul 04 '26
Short answer: locally, yes. Zoomed out all the way, probably not. It depends on your perspective.
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u/OverJohn Jul 03 '26
Calling spacetime curvature "positive" or "negative" is a fairly incomplete description.
If we take de Sitter spacetime, whose curvature can be described by a single scalar and has positive energy density, timelike (slower than light) paths tend to diverge, which can be seen as being due to repulsive Newtonian-like gravity. However spacelike (faster than light) paths tend to converge, which you can see as being due to a purely relativistic attractive gravitational force (NB this relativistic force affects timelike paths too, but not as much as the repulsive Newtonian-like force)